Spectacle device with an adjustable field of view and method

ABSTRACT

The invention relates to a spectacle device ( 1 ) for capturing at least one parameter of at least one eye ( 10   l,    10   r ) of a test person ( 31 ) wearing the spectacle device ( 1 ), the spectacle device ( 1 ) comprising a frame ( 4 ) configured to fix the spectacle device ( 1 ) to the head of the test person ( 31 ), at least one first capturing unit ( 3   l,    3   r ) configured to optically capture the at least one parameter of the at least one eye ( 10   l,    10   r ), and a second capturing unit ( 2 ) the optical capture range of which at least partly corresponds to an optical capture range of the at least one eye ( 10   l,    10   r ) and which is configured to output data concerning a field of view (FOV 1,  FOV 2 ) which is correlated with the optical capture range of the second capturing unit ( 2 ), wherein the field of view (FOV 1,  FOV 2 ) is adjustable.

The invention relates to a spectacle device for capturing at least oneparameter of at least one eye of a test person wearing the spectacledevice, the spectacle device comprising a frame configured to fix thespectacle device to the head of the test person, at least one firstcapturing unit configured to optically capture the at least oneparameter of the at least one eye, and a second capturing unit theoptical capture range of which at least partly corresponds to an opticalcapture range of the at least one eye and which is configured to outputdata concerning a field of view which is correlated with the opticalcapture range of the second capturing unit. The invention also relatesto a method for capturing at least one parameter of at least one eye ofa test person by means of a spectacle device.

It is known from the prior art to use head mounted eye tracker devices.US RE39,539 E discloses an apparatus for monitoring movement of aperson's eye. The system includes a frame that is worn on a person'shead, an array of emitters on the frame for directing light towards theperson's eye, and an array of sensors on the frame for detecting lightfrom the array of emitters. The sensors detect light that is reflectedoff of respective portions of the eye or its eyelid, thereby producingoutput signals indicating when the reflective portion of the eye iscovered by the eyelid. The system allows to monitor the persons level ofdrowsiness.

U.S. Pat. No. 6,163,281 discloses a system and method for communicationusing movement of a person's eye, including an emitter for directinglight towards an eye, a sensor for detecting emitted light from theemitter, and a processor coupled to the sensor for converting sequentiallight intensity signals received from the sensor to a stream of data,and/or for converting the signals into an understandable message.

US 2004/0196433 A1 discloses an eye tracking system for monitoring themovement of a user's eye comprising an eye camera and a scene camera forsupplying to interlace electronics video data indicative of an image ofthe user's eye and an image of the scene observed by the user. Inaddition, the system incorporates a frame grabber for digitizing thevideo data and for separating the eye and scene data into two processingchannels, and a spot location module for determining from the video datathe location of a reference spot formed on the user's eye byillumination of the user's eye by a point source of light. The systemfurther incorporates a pupil location module in order to determine theuser's line of gaze.

WO 2010/83853 A1 discloses a gaze point detection system with one ormore infrared signal sources to be placed in a test scene as referencepoints, at least one pair of eye glasses worn by a test subject, and adata processing and storage unit for calculating a gaze point of theperson. The eye glasses comprise an image sensor adapted to detect IRsignals from the at least one IR signal source and to generate an IRsignal source tracking signal, an eye tracking unit adapted to determinethe gaze direction of the test subject person and to generate an eyetracking signal, and a camera unit adapted to acquire a test scenepicture.

WO 2004/066097 A2 discloses an eye tracking system for displaying avideo screen pointer at a point of regard of a users gaze. The systemcomprises a camera focused on the user's eye, a support connected to thecamera for fixing the relative position of the camera to the user'spupil, and a computer having a CPU and an eye tracking interface. Bydetermining the center of the eye, a pointer on the video display screencan be displayed at the point of regard.

US 2010/0220291 A1 discloses an eye tracking system with a transparentlens, at least one light source, and a plurality of light detectors. Thetransparent lens is adapted for disposal adjacent an eye. At least onelight source is disposed within the transparent lens and is configuredto emit light towards the eye. The at least one light source istransparent to visible light. The plurality of light detectors isdisposed within the transparent lens and is configured to receive lightthat is emitted from the at least one light source and is reflected offof the eye. Each of the light detectors is transparent to visible lightand is configured, upon receipt of light that is reflected off of theeye, to supply an output signal. US 2010/0220291 A1 discloses an opticalmeasuring device according to the preamble of the present application.

The head mounted eye tracker disclosed in US 2010/0220291 A1 uses acamera that captures the scene in the gaze direction of the eye. Thegaze direction of the eye, captured by another camera-like device, canthen be correlated with the scene pictures acquired by the scene camera.However, the present spectacle devices merely allow to correlate thecaptured scene with the gaze direction within very limited boundaries.Thus, reliable eye tracking may be compromised. Consequently, known headmounted eye tracker devices usually suffer from a limited accuracy androbustness.

An object of the present invention is to provide a spectacle device anda method which allow for more reliable correlation between a capturedparameter of at least one eye of a test person with an optical capturerange of the at least one eye.

This task according to the invention is solved by a spectacle devicehaving the features according to patent claim 1 and a method having thefeatures according to patent claim 12. Advantageous embodiments of theinvention are the subject-matter of the independent claims and thedescription.

The spectacle device according to the invention serves for capturing atleast one parameter of at least one eye of a test person wearing thespectacle device. The spectacle device comprises a frame configured tofix the spectacle device to the head of the test person, at least onefirst capturing unit configured to optically capture the at least oneparameter of the at least one eye, and a second capturing unit theoptical capture range of which at least partly corresponds to an opticalcapture range of the at least one eye and which is configured to outputdata concerning a field of view which is correlated with the opticalcapture range of the second capturing unit. According to the inventionthe field of view is adjustable.

This way it is possible to more reliably correlate the capturedparameter of the at least one eye with the optical capture range of theat least one eye. The test person may observe a scene with a field ofview defined by the physiological capture range of its eyes. This fieldof view is usually much larger than the field of view capturable by thesecond capturing unit, the later being technically limited. Not eachgaze direction of the test person may then fall into the capturablefield of view of the second capturing unit. However, by making the fieldof view of the second capturing unit adjustable a field of view thatcorresponds to the respective gaze direction can be chosen. Even in caseof extreme viewing angles of the eyes a correlation of the gazedirection with the scene captured by the second capturing unit becomespossible. Even if the viewing direction strongly deviates from astraight ahead viewing direction eye-tracking is still possible.

In particular, the spectacle device forms an optical measuring device.The frame may resemble the frame of conventional eye-glass lenses. Thefirst capturing unit may comprise at least one camera. Also the secondcapturing unit may comprise at least one camera, which can serve as ascene camera. The optical capture range of the at least one eye of thetest person can be defined as a field of view observable by the testperson for the eyes being fixed in a position corresponding to aspecific viewing direction. The optical capture range of the secondcapturing unit may be a field of view of the second capturing unit for aspecific orientation of the spectacle device in space. In particular,the optical capture range of the second capturing unit and the at leastone eye may overlap.

In one preferred embodiment the field of view is automaticallyadjustable in dependency on the at least one captured parameter of theat least one eye. In particular, the field of view may be automaticallyadjusted in dependency on the gaze direction of the at least one eye.The field of view may change from a portrait orientation to a landscapeorientation or vice versa. In particular, if the test person moveshis/her eyes sideways or gazes sideways a landscape orientation for thefield of view can be chosen, while for the test person looking upwardsor downwards a portrait orientation for the field of view can beautomatically selected. This embodiment guarantees that for a specificparameter of the at least one eye the field of view is chosen such thatit can be easily correlated with this captured parameter.

In another embodiment the field of view is manually adjustable, inparticular by the test person. The test person can then choose the fieldof view which is most adequate in the respective situation.

Advantageously, the second capturing unit is arranged tiltably and/orrotatably within the frame, in particular rotatably about its opticalaxis. The field of view is than adjustable by tilting or rotating of thesecond capturing unit. For this purpose the second capturing unit maycomprise movable elements. In particular, an optical element, forexample a prism and/or a lens, may be rotatably arranged on the opticalaxis of the second capturing unit, wherein by a rotation of the opticalelement, the field of view is adjustable. This is a very simple means ofadjusting the field of view of the second capturing unit. Despite beinga cheap solution the field of view can be adjusted in a very reliablefashion.

Advantageously, the second capturing unit can comprise at least twosubunits of the capturing unit which differ with regard to theirrespective field of view. The field of view of the second capturing unitis then adjustable due to the data captured by the subunits of thecapturing unit being separately analyzable and/or due to the subunits ofthe capturing unit being separately controllable. This embodiment hasthe advantage that it does not necessarily require mechanically movableparts. The two subunits together can provide data that can be merged toprovide a resulting or effective field of view. One subunit can forexample be adjusted such that it captures a portrait field of view whilethe other subunit may be oriented in such a way that it captures alandscape field of view. Only one or the other subunit may be read outat the same time.

Advantageously, the sub-units of the capturing unit have different focallengths and in particular a first of the at least two sub-units of thecapturing unit comprises telephoto lens optics and/or a second of the atleast two sub-units of the capturing unit comprises wide-angle lensoptics. These are effective technical means to acquire different fieldof views.

Advantageously, the second capturing unit comprises at least onetwo-field lens and/or at least one progressive multi-focal lens and/orat least one prism and/or at least one free form lens, in particular aconical mirror. The different optical elements allow to capturedifferent fields of view which may or may not be distorted with regardto planarity. Depending on the chosen optical element the field of viewcan be adjusted to the respective observation condition.

In another embodiment the second capturing unit may comprise a detectorwith a pixel array and the adjusting of the field of view is effected bya selection of the pixels the data of which are captured. A selection ofpixels can result in a choice of a region of interest. In particular,only the pixels which relate to the desired field of view may be readout. The aperture angle of a field of view can be varied by the sizeand/or position of a region of interest. This way, the volume of data,which needs to be processed, is kept low. Superfluous data andredundancy is avoided. Only such information is acquired which isactually necessary to correlate the at least one parameter of the atleast one eye with the capture range of the second capturing unit. Ifthe pixel array of the second capturing unit is quadratic a rectangularsub-array with portrait or landscape orientation can be chosen. This waythe field of view can be adjusted very easily. Advantageously, in orderto keep the resolution of the sensor data constant, an additionalscaling step an/or a pixel-binning may be employed.

Advantageously, the at least one first capturing unit and/or the secondcapturing unit and/or one of the at least two subunits of the capturingunit comprises at least one camera.

Advantageously, the at least one captured parameter concerns anorientation and/or a position and/or an eyelid closure and/or a pupildiameter and/or a sclera characteristic and/or an iris characteristicand/or a characteristic of a blood vessel and/or a cornea characteristicof the at least one eye. In particular the at least one capturedparameter may concern a cornea radius (anterior, posterior), an eyeballradius, a distance pupil-center to cornea-center, a distancecornea-center to eyeball-center, a distance pupil-center to limbuscenter, a cornea keratometric index of refraction, a cornea index ofrefraction, a vitreous humor index of refraction, a distance crystallinelens to eyeball-center and to cornea center and to corneal apex, acrystalline lens index of refraction, a visual axis orientation, anoptical axis orientation, a pupil axis (achromatic axis) orientation, aline of sight orientation, an astigmatism degree (diopters) andorientation angle of flat and steep axis, an iris diameter, pupildiameters (pupil major and minor axes), pupil area), limbus major andminor axes, eye cyclo-torsion, eye intra-ocular distance, eye vergence,statistics over eye adduction/abduction and statistics over eyeelevation/depression. The spectacle device can then work as an eyetracking device.

Advantageously, the second capturing unit is integrally connected to theframe and/or structurally integrated in the frame. The second capturingunit may be a camera built into the frame. It may also be a cameraattached to the frame. In a preferred embodiment the second capturingunit is placed above a nose piece element of the spectacle device inbetween two frame parts framing eye-glass lenses. In particular, thesecond capturing unit is placed close to the at least one eye of thetest person when the spectacle device is fixed to the head of the testperson. This embodiment guarantees that the overlap region of the fieldof view of the test person and the field of view of the second capturingunit is very good.

Advantageously, the frame comprises at least a first and a second frameelement, wherein the second capturing unit is attached to the secondframe element, and wherein the second frame element is pivotably hingedto the first frame element, and wherein the first frame element isformed in particular as an arm. The spectacle device then particularlyhas the form of conventional eye-glass lenses with a main frame partforming the second frame element and two arms forming the first frameelement, which allow to fix the spectacle device on and/or behind theears of the test person. This way the sight of the second capturing unitonto the scene observable by the test person is unperturbed. Unusualadd-ons that may disturb the test person are avoided.

The method according to the invention serves for capturing at least oneparameter of at least one eye of a test person by means of a spectacledevice. The method comprises the following steps:

-   -   optically capturing the at least one parameter of the at least        one eye by means of at least one first capturing unit;    -   capturing an optical capturing range by means of a second        capturing unit, wherein this optical capturing range corresponds        at least partly to an optical capturing range of the at least        one eye;    -   outputting data concerning a field of view by the second        capturing unit, wherein the field of view is correlated with the        optical capturing range of the second capturing unit; and    -   adjusting the field of view by means of an adjustment means of        the spectacle device.

Advantageously, the adjustment means is structurally integrated in thespectacle device. Advantageously, the field of view is automaticallyadjusted in dependency on the at least one captured parameter of the atleast one eye.

Advantageously, the field of view is automatically adjusted independency on data concerning the kind of an object captured by thesecond capturing unit and/or a characteristic of the object and/or adistance of the object from the second capturing unit and/or anorientation of the object relative to the second capturing unit. If theobject, for example, is oriented in a horizontal direction to thespectacle device a landscape field of view can be automatically chosen.If the orientation of the object is vertical, a portrait field of viewmay be automatically selected. The outer appearance of the object thendetermines the most suitable field of view to guarantee reliableeye-tracking.

Advantageously, the field of view is adjusted in such a way that by theset of the adjustable fields of view a resulting field of view iscovered that essentially corresponds to the physiological field of viewof a human being. The field of view of the second capturing unit may betechnically limited. By particular adjustment means, however, this fieldof view can be changed, for example, with regard to its orientation,such that all fields of view taken together essentially cover a largerresulting field of view. In particular, the data corresponding to thedifferent fields of view may be merged to derive a large field of view.

Further features of the invention derive from the claims, the figures,and the description of the figures. All features and featurecombinations previously mentioned in the description as well as thefeatures and feature combinations mentioned further along in thedescription of the figures and/or shown solely in the figures are notonly usable in the combination indicated in each case, but also indifferent combinations or on their own.

The invention is now explained in more detail with reference toindividual preferred embodiments and with reference to the attacheddrawings. These show in:

FIG. 1A a front view of a spectacle device according to an embodiment ofthe invention;

FIG. 1B a side view of the spectacle device of FIG. 1A;

FIG. 1C a top view of the spectacle device of FIG. 1A;

FIG. 1D a perspective view of the spectacle device of FIG. 1A;

FIG. 2 a rear view of a spectacle device;

FIG. 3 a schematic rear view of a spectacle device with an eye cameramaking use of a deflection element to direct its optical path onto theeye;

FIG. 4 a side view of a spectacle device schematically showing theorientation of an eye camera;

FIG. 5 a schematic view of individual electronic components comprised bya spectacle device;

FIG. 6A a picture with a symbol indicating a large parallax errorattained with an optical measuring device according to the prior art;

FIG. 6B a picture showing a symbol indicating the lack of a parallaxerror with a spectacle device according to an embodiment of theinvention;

FIG. 7 a parallax error model;

FIG. 8 a diagram comparing parallax errors of measuring devicesaccording to the prior art and according to an embodiment of theinvention;

FIG. 9A a first field of view acquired by a scene camera;

FIG. 9B a second field of view acquired by the scene camera;

FIG. 10A a schematic side view of a spectacle device were the opticalpath of an eye camera extends in a straight line from the eye camera toan eye; and

FIG. 10B a schematic side view of a spectacle device where the opticalpath of an eye camera extends from the eye camera via a mirror to theeye.

In the figures same elements or elements of the same function areequipped with the same reference signs. FIGS. 2, 3, and 4 show the samereference frame with a Cartesian coordinate system and perpendicularaxes x, y and z.

FIGS. 1A to 1D show an optical measuring device which has the form of aspectacle device 1 or eye tracking device, respectively. The spectacledevice 1 is designed such that a person can wear it on its head justlike a normal pair of glasses. It comprises a frame 4 with two side bars5 l and 5 r which support the spectacle device 1 on the ears of theperson who is wearing it. Furthermore, the spectacle device 1 is held inplace on the head by a nose support 7. The mainframe has a specificwidth w1 and height h. Its length 1 depends on the length of thesidebars 5 l and 5 r. As can be seen in FIG. 1C the sidebars 5 l and 5 rare hinged to the front part of the frame 4 such that the distance w2between the side bars 5 l and 5 r can be enlarged or reduced (see dashedsidebar configuration for sidebar 5 l in FIG. 1C).

Alternatively, the optical measuring device may not be designed in formof a regular pair of eye glasses, but may be designed such that itresembles a helmet, forming a frame, with a face shield, forming a frameinsert.

Above the nose support 7 in the frame 4 a scene camera 2 is installed.It can either be attached to or integrated into the frame 4. With thescene camera 2 virtually a similar field of view can be captured as seenby a test person when wearing the spectacle device 1. In the lower partof the frame 4 the spectacle device 1 contains two eye cameras 3 l and 3r. When the spectacle device 1 is worn by a person the person's eyes canbe captured by the eye cameras 3 l and 3 r, which are integrated intothe frame 4 at a suitable angle. Eye cameras 3 l and 3 r are designed toobserve the person's left eye and right eye, respectively, i.e. capturecharacteristics of the person's eyes.

The frame 4 contains two openings which are filled with eye glass lenses8 l and 8 r thus forming frame inserts. The pictures acquired by thescene camera 2 and the eye cameras 3 l and 3 r lead to signals which areprocessed in one or several pre-processing units 6 integrated into thesidebars 5 l and 5 r.

FIG. 2 shows an inside view of the spectacle device 1. Along the rim ofthe frame part enclosing the eye glass lenses 8 l and 8 r several LightEmitting Diods (LEDs) 9 are located in a ring arrangement. When thespectacle device 1 is worn by a person, those LEDs 9 can illuminate theeyes of the test person in a defined way. The LEDs 9 will causereflections on the eyes of the test person (cornea reflections) for allpossible gaze angles. Those reflections can be detected by the eyecameras 3 l and 3 r and can be used for eye tracking.

The LEDs 9 can be switched on an off individually, in groups or alltogether following a specific time pattern, strobe characteristic orspatial variation. The on-off-switching-frequency of different LEDs 9 orgroups of LEDs 9 may vary. Certain groups of LEDs 9 may get switched onexactly when other groups of LEDs 9 get switched off. A specific spatialand temporal correlation pattern may be implemented with regard to theswitching and thus illumination characteristics. This way a reflectionpattern can be created on the eyes that can be recognized easily by theeye cameras 3.

The overall setup with the most important electronic components is shownin FIG. 5. The eye cameras 3 l and 3 r are connected to specific cameraelectronics 15 by 100 mm long cables 14. In particular, the cameras 3 land 3 r comprise only basic electronic components while their majorelectronic components are located within the camera electronics 15. Thisway, the primarily “optical part” of the cameras 3 l and 3 r can belocated remote to the primarily “electronic part” within the cameraelectronics 15. Both parts can then be connected by flex-PCB cables 14.This way, the optical sensor and the basic electronic components withinthe cameras 3 l and 3 r form a very small and highly compact entitywhile bulkier electronic components within the electronics 15 can beplaced on more spacious integrated circuit boards elsewhere. Theelectronics 15 are connected to a pre-processing unit 16 which canprocess the signals from the eye cameras 3 l and 3 r. The pre-processingunit 16 can be identical to the pre-processing unit 6 located in thesidebars 5 l and 5 r of the spectacle device 1. The pre-processing unit16 is connected to a USB-hub 19. The LEDs 9 installed in the frame 4form a first and a second IR LED chain 21 and 22 arranged in a ringconfiguration around the eye glass lenses 8 l and 8 r. The IR LED chains21 and 22 are connected to an IR LED constant current source 20, whichis also connected to the USB-hub 19. The USB-hub 19 additionally servesas a power source for the IR LED constant current source 20. The LEDs 9of the IR LED chains 21 and 22 can be switched on an off individually.To achieve this, they may be connected to the IR LED constant currentsource 20 in a parallel network with individual electrical switches foreach LED 9 being implemented.

The USB-hub 19 is connected via a USB 2.0 cable 25 to a pre-processingunit 26. The signals pre-processed in the pre-processing unit 26 arefinally analyzed in a personal computer 27, which contains a recorderdevice 28. An additional aux-/sync-port 13 forming an interface on thespectacle device 1 can also be connected to the USB-hub 19. Theaux-/sync-port 13 can serve as interface for synchronization with otherelectronic devices or for triggering parallel data acquisitions. Theelectronics 15, pre-processing unit 16, USB-hub 19 and IR LED constantcurrent source 20 are located on a common printed circuit board PCB 23.

In analogy to this setup the scene camera 2 is also connected toelectronics 15 via a 100 mm cable 14. In this case the electronics 15are located on a second printed circuit board PCB 24, which alsocontains a pre-processing unit 17. The pre-processing unit 17 can bebased on electronics according to the DaVinci digital signal processor(DSP). It contains an MPEG encoder 18 for encoding the signals receivedfrom the electronics 15. A microphone 12 may also be connected to thepre-processing unit 17. The pre-processing unit 17 located on the PCB 24is connected to the USB-hub 19. This way, processing signals acquired bythe scene camera 2 are finally analyzed in the personal computer 27.

The pre-processing units 6, 16, 17 and 26 may be able to compress atleast one of the three image streams generated by the two eye cameras 3l and 3 r and the scene camera 2. Here, different alternatives arepossible. A pre-processing unit may compress only the image stream ofone camera while each camera has its own pre-processing unit.Alternatively, a single pre-processing unit may compress the imagestreams of all cameras. Furthermore, the pre-processing units may beconfigurable via a system interface and corresponding software to managethe bandwidth by adjustment of resolution, region of interest, framerate and compression parameters. The pre-processing units may bedesigned to trigger synchronously the camera's image acquisition. Theymay provide time stamps for each acquired image which can be used tosynchronise several or all camera data streams offline.

The pre-processing units may either be located on integrated circuitboards of the cameras or on a separate integrated circuit board that islocated at or on a head mount (e.g. in the side bar 5 l or 5 r of thespectacle device 1) or in a separate housing that is worn by the testperson 31, e.g. on a belt.

The spectacle device 1 may also comprise an auxiliary interface whichallows to acquire data in real time from external sensors. Such sensorsmay be biometric sensors (including but not limited to EEG, ECG, etc.)or attitude sensors (including but not limited to accelerometers,magnetometers, gyroscopes, etc.). It is then possible to synchronise thedata stream of the external sensors with the data streams acquired fromthe cameras 2, 3 l and 3 r. Furthermore, an external clock or triggersignal can be provided that can be used by the external sensors tosynchronise themselves with the system. The bandwidth of data acquiredfrom the interface can be reduced or compressed by means of on-boardprocessing resources integrated in the system in its dedicated recordingunit 28.

The eye cameras 3 l and 3 r can either be suited for visible or nearinfrared light. They are located symmetrically with respect to avertical centre line that divides the user's face into two halves. Theeye cameras 3 l and 3 r may be positioned in front and below the eyes 10l and 10 r respectively, for example in or at the lower rim of a pair ofeye glass lenses 8 l and 8 r, pointing at the eyes 10 l and 10 r in anangle of 30° to 50° and being mounted in the frame 4 in an angle a of30° to 50°. In the embodiment the eye cameras 3 l and 3 r are sensitivein the near infrared.

The scene camera 2 can be located on a vertical centre line that dividesthe user's face into two halves in or at the nose bridge of the frame 4.Alternatively, it may also be located at, in or close to the rim of ahelmet, cap or headband. The scene camera 2 may have HD (highdefinition) and/or adjustable resolution of at least 720 p (1280×720pixels) and is operated at 30 Hz or 60 Hz. It can either be mounted inlandscape or portrait orientation. Furthermore, it can be mounted suchthat its orientation can be changed from landscape to portraitorientation (camera roll) and also the direction the camera is pointingin (camera pan and tilt).

Instead of a single scene camera 2, the spectacle device 1 can alsocomprise a pair of scene cameras, where each scene camera can beoriented either in portrait mode or in landscape mode. Furthermore, eachscene camera can be oriented independently of the respective secondscene camera. Alternatively, both scene cameras 2 may have fixedorientations, which may or may not differ from each other.

Furthermore a prism or lens can be mounted in front of the scene camera2 to create a different positioning of the field of view of the scenecamera 2 with respect to the glasses, especially a more downwardoriented field of view for near range reading applications.

Six LEDs 9 are located around each eyeglass lens 8. They emit in theinfrared wavelength range (typically above 750 nm and below 1000 nm) ata central wavelength of 850 nm. They are driven by 50 mA currentprovided by the IR LED constant current source 20.

Instead of direct illumination of the eyes with the LEDs 9 also animplementation with a light guide can be envisaged. One or severalsegments of light guides (e.g. fiber optics) may be used. Theillumination of the eyes may be implemented with focusing optics(structured illumination). Instead of the LEDs 9 suitable diffractiveoptics or lasers may be used to generate a pattern of coherent light forilluminating the eyes. The light source can be used together with anoptical element in order to create a pattern of reflections on the eyes10 l and 10 r (e.g. with focusing optics or diffractive optics). Theillumination source may either emit visible or near infrared light. Theillumination source may be positioned in or on the frame 4, inparticular in a circle-like arrangement around the eye glass lenses 8 land 8 r. Alternatively, the illumination source may be located on therim or frame of a head mounted display. It may specifically be designedto create a pattern of reflections on the eye surfaces of the testperson 31.

When the spectacle device 1 shown in FIG. 2 is worn by a test person thesituation shown in FIG. 10A in a simplified way is realized. The eyecamera 3 is arranged in such a way on the frame 4 that with thespectacle device 1 fixed to the head of a test person the optical path Mcapturing at least one parameter of the eye 10 extends in a straightline from the eye camera 3 to the eye 10.

FIGS. 3 and 10B show a different configuration of the spectacle device1. The spectacle device 1 comprises a mirror 11, forming an opticaldeflection element attached to the frame 4, the mirror 11 and the eyecamera 3 being arranged in such a way on the frame 4 that with thespectacle device 1 fixed to the head of the test person the optical pathM for capturing at least one parameter of the eye 10 extends from theeye camera 3 via the mirror 11 to the eye 10. The three dimensionalrepresentation of FIG. 3 shows the spectacle device 1 from a rear orinside view. In the figure, reflections of the left and right eye 10 land 10 r, respectively, show in the eyeglass lenses 8 l and 8 r. Thecoordinate system is a Cartesian one with the z-axis being directed intothe plane of projection.

Thus, the eye cameras 3 l and 3 r may be mounted in front of and abovethe eyes 10 l and 10 r with an optical guide or mirror 11 located infront and below the eyes 10 l and 10 r, for example in or at the lowerrim of a pair of eye glass lenses 8 l and 8 r in order to acquire animage of each eye 10 l and 10 r from a forward and low perspective andto make that image visible to the eye cameras 10 l and 10 r. The opticalguide or mirror 11 can either be a (flat) mirror, a spherical mirror, adome, a custom lens, a holographic image guide, etc. The mirror 11 canbe reflecting only a specific range of wavelength and be transparent toothers.

The mirror 11 can either be a flat mirror or a spherical mirror. Theadvantage of a spherical mirror is that it magnifies the field of viewof the eye camera 3 beyond the field of view achievable with a flatmirror. The configuration of FIG. 3 furthermore allows to place theoptical system very close to the eye 10 (set direction) thus improvingergonomics and aesthetics. The test person's own field of view is hardlyobstructed. The mirror 11 can be a so-called hot mirror, i.e. the mirror11 is transparent in the visible wavelength range while having a higherreflectivity in the infrared wavelength range. It can be very thin andhollow (so-called dome) thus, minimizing the distortion due torefraction. It can be made out of a material showing a very low index ofrefraction (IOR).

In both cases (FIGS. 10A and 10B) the eye camera 3 is arranged in such away that the optical path M for the capturing of at least one parameterof the eye 10 excludes the frame insert, i.e., the eye glass lens 8.Furthermore, the eye glass lens 8 is arranged in such a way that theoptical axis K of the eye 10 and the optical path M as single jointlyused optical element comprise the eye 10. Furthermore, the optical pathM entirely runs within a space Sp which extends on the side of the eyeglass lens 8 facing the eye 10.

The embodiments shown in FIGS. 2 and 3 and FIGS. 10A and 10B,respectively, both reduce eye occlusion due to the upper eye-lid.

FIGS. 6A to 8 illustrate the reduction of parallax errors in thespectacle device 1 compared to the prior art. As can be seen in FIG. 6Athe position of an object 29 the test person actually focuses its eyeson and the point of regard 32 determined by the spectacle device 1usually do not coincide very well when using spectacle devices 1 asknown from the prior art. This effect is usually the more pronounced thecloser the test person is located to the object 29 that is to befocused. However, with the spectacle device 1 according to an embodimentof the invention the coincidence between the determined point of regard32 and the actual object 29 is very good, even for measuring distancesas low as 0.5 m (see FIG. 6B). This is achieved by minimizing thedistance between the eye ball center and the camera focal point.

The situation is again illustrated in FIG. 7. As eye 10 and scene camera2 are located at slightly different positions the difference in theirrespective viewing angles for focusing the object 29 becomes the morepronounced the closer the object 29 is located to the eye 10 and scenecamera 2, respectively (i.e. larger distortions for smaller z-values).The spectacle device 1 may get calibrated in the situation shown in FIG.6B. The object 29 then lies in the calibration plain P and bycalibrating the spectacle device 1 one can make sure that the determinedpoint of regard 32 indeed falls onto the actual object 29. Calibrationis typically performed on a plane at some distance from the testsubject. It relates measured gaze direction (angles) to pixels in thescene video frame. This calculation gives valid results only for pointsthat lie in that calibration plane. For points that do not lie on thatplane, a systematic error (parallax) is introduced. When the distance ofthe spectacle device from the object 29 is increased the differencebetween the distance to the calibration plain P and the actual distanceto the object 29 causes the pronounced deviations. With the spectacledevice 1 according to an embodiment of the invention these deviations orparallax errors (indicated by symbols S2, circles, in FIG. 8) for alldistances d are considerably smaller than with devices according to theprior art (symbols S1, rectangles). Thin-lined crosses relate to thegroup of symbols S2, while bold crosses relate to the group of symbolsS1. The crosses correspond to the point of regard 32 used forcalibration purposes.

The parallax error is mathematically modelled as a function of theposition of the scene camera 2 with respect to the eye position. Thegaze estimation error due to parallax is minimized by placing the scenecamera 2 as close as possible to the eye 10, according to the resultsshown by the mathematical simulation. The parallax error can be furthercorrected by estimating the distance to the point of regard by usingvergence from binocular tracking and by estimating the position of theeyes with respect to the eye tracking device.

To achieve even better results the field of view of the scene camera 2can be optimized. The scene camera 2 with standard optics has a field ofview that does not cover the full physiological gaze range (horizontalfield of view of standard optics: 40° to 50°; typical physiological gazerange: 60°). In an embodiment the field of view of the scene camera 2can thus be optimized depending on the respective application. One suchfield of view optimization method is illustrated in FIGS. 9A and 9B. Auser wearing the spectacle device 1 is at the same time observing abackground B and his mobile phone 30. According to FIG. 9A the field ofview FOV1 mainly covers the background B. When the test person 31 looksdown onto its mobile phone 30 the change in gaze direction isautomatically determined by the eye cameras 3 l and 3 r and the scenecamera's 2 field of view is automatically adjusted by switching fromlandscape to portrait orientation (field of view FOV2). This can beachieved by a z-axis 90° mechanical roll of the scene camera 2 or by theuse of an optical prism in front of the scene camera 2. Also the use oftwo scene cameras with different tilt or roll angles is possible.Alternatively, also an optical beam splitter may be used in front of thescene camera 2.

In summary, the spectacle device 1 forms a head-mounted eye trackingsystem which consists of three cameras: two eye cameras 3 l and 3 r andat least one scene camera 2. The three cameras 3 l, 3 r and 2 can have amanageable bandwidth, for example by adjustable frame rates orresolutions. One or several pre-processing units 6, 16, 17 and 26 mayexist that perform variable compression of the video streams receivedfrom the cameras 2, 3 l and 3 r. The level of compression of the videostreams may be the same for the eye cameras 3 l and 3 r and the scenecamera 2, or the video streams may be separately compressed for the eyecameras 3 l and 3 r and the scene camera 2. The frame rate for eyecamera 3 l may correspond to full speed acquisition, the one of eyecamera 3 r may correspond to 1/10 speed acquisition and the one for thescene camera 2 may correspond to ½ speed acquisition. Instead ofadjusting the frame rates of the different cameras, alternatively theacquisition rates may be chosen to be the same, while data processing isperformed differently for each camera. Data provided by one camera maybe compressed more than data provided by another camera, although bothcameras acquire the same amount of data. One may also combine differentcompression rates with different acquisition rates. It is also possibleto omit, for example, every second acquired image when transferring thedata and thus reduce the amount of data to be sent to the CPU by half.The signals of the cameras 2, 3 l and 3 r may be transferred to a CPU inthe PC 27 via a wired or wireless interface (see FIG. 5). Auxillaryinterfaces for other data sources and methods for synchronisation withthese data sources may be implemented in the spectacle device 1.

The spectacle device 1 can come as a system comprising severalexchangeable pieces. The spectacle device 1 can have an exchangeable setof nose pieces or nose supports 7 for faces with small or large noses.This way, the spectacle device 1 can be worn over vision correctionglasses without a problem. Furthermore, the spectacle device 1 has aholding mechanism for exchangeable glasses that can have differentlevels of light transmittance (e g. clear glasses or sun glasses) for acertain range of wavelengths. Additionally or alternatively theexchangeable glasses can have a near infrared optical filter to matchthe wavelength of the illumination source and block some or all lightfrom the outside of same and similar wavelengths from reaching the eyesurface to improve signal to noise on the eye surface. The spectacledevice 1 has rims and a nose bridge that serve as a mount or housing forthe eye cameras 3 l and 3 r and the scene camera 2. The eye cameras 3 land 3 r are mounted in such a way that their field of view extendsbehind the exchangeable glasses 8 l and 8 r.

With the spectacle device 1 it is possible to do eye tracking,occulometrics, biometrics and position and motion measurements in orderto measure and classify as fully as possible human behaviour in a freerange movement setup. A head mounted eye tracking device is realisedwhich is calibration-free and provides an astigmatism estimation. Theeye-tracking functionality has zero set-up time. No adjustments arenecessary. A test person 31 can just put the spectacle device 1 on andstart using it. It has a very large gaze-tracking range covering thephysiological range of human eye movement (80° horizontal, 60°vertical). It is very robust and has a high accuracy in gaze mapping.Astigmatism is compensated for, parallax is minimized, pupil axis shiftis compensated and the device is calibration free or can be calibratedusing a one-point calibration feature. Furthermore, it is designed towork irrespective of ethnic group (Caucasian, Asian, African, etc.),gender and age. The field of view of the scene camera 2 is optimized. Bythe use of optical, inertial or magnetic sensors a head trackingfunctionality can be implemented. The spectacle device furthermoreoffers biometric features, such as measuring the pupil diameter andoffering interfacing and synchronisation options with EEG, ECG, etc.Finally, it can be integrated with a head mounted display. It ispossible to project a virtual image onto a subject's eye of a portablecomputer screen. Furthermore, the possibility is offered to interactwith “objects” in the virtual image using eye movement (gaze, blinks).

Head tracking functionality can be realized by the use of three axisgyroscopes, three axis accelerometers and/or three axis magnetometerswith optional sensor fusion for six dimensional head tracking.

In summary, the spectacle device 1 offers a very specific optical andelectronic architecture. With respect to the electronic architecturethree or more high resolution cameras with allocateable bandwidth areincorporated in the device 1. Separate processing channels for eyecameras 3 l and 3 r and the scene camera 2 are envisaged. The opticalarchitecture is characterized by exchangeable glasses with variousproperties. The optical path of the eye cameras 3 l and 3 r extendsbehind the glasses or eye glass lenses 8 l and 8 r respectively.Furthermore, a set of LEDs 9 allows for highly variable illumination ofthe eyes 10 l and 10 r. For instance, the illumination geometry aroundthe eye can be controlled. The specific LED subsets can be controlledwith regard to strobe effect and sequencing. Finally, eye illuminationcan be achieved by point, line or two-dimensional light sources.

REFERENCE SIGNS

1 spectacle device

2 scene camera

3, 3 l, 3 r eye camera

4 frame

5 l, 5 r side bar

6 pre-processing unit

7 nose support

8, 8 l, 8 r eyeglass lens

9 LED

10, 10 l, 10 r eye

11 mirror

12 microphone

13 aux-/sync-port

14 cable

15 electronics

16 pre-processing unit

17 pre-processing unit

18 MPEG encoder

19 USB hub

20 IR LED constant current source

21, 22 IR LED chain

23, 24 PCB

25 USB 2.0 cable

26 pre-processing unit

27 PC

28 recorder

29 object

30 mobile phone

31 test person

32 point of regard

w1, w2 width

h height

I length

a tilt angle

K optical axis

M optical path

O origin of system of reference

P calibration plane

Sp space

d distance

S1, S2 symbols

B background

FOV1, FOV2 field of view

x, y, z axis

1.-15. (canceled)
 16. A spectacle device for capturing at least oneparameter of at least one eye of a test person wearing the spectacledevice, the spectacle device comprising a frame configured to fix thespectacle device to the head of the test person, at least one firstcapturing unit configured to optically capture the at least oneparameter of the at least one eye, and a second capturing unit having anoptical capture range which at least partly corresponds to an opticalcapture range of the at least one eye, characterized in that the secondcapturing unit is configured to output data concerning a field of viewof the second capturing unit whereby the field of view is correlatedwith the optical capture range of the second capturing unit for aspecific orientation of the spectacle device in space, and whereby,further on, the field of view of the second capturing unit isadjustable.
 17. The spectacle device according to claim 16,characterized in that the field of view is automatically adjustable independency on the at least one captured parameter of the at least oneeye.
 18. The spectacle device according to claim 16, characterized inthat the field of view is manually adjustable, in particular by the testperson or an operator.
 19. The spectacle device according to claim 16,characterized in that the second capturing unit is arranged tiltableand/or rotatable within the frame, in particular rotatable about itsoptical axis, and in that the field of view is adjustable by a tiltingor rotating of the second capturing unit.
 20. The spectacle deviceaccording to claim 16, characterized by an optical element, inparticular a prism and/or a lens, rotatably arranged on the optical axisof the second capturing unit, wherein by a rotation of the opticalelement the field of view is adjustable.
 21. The spectacle deviceaccording to claim 16, characterized in that the second capturing unitcomprises at least two sub-units of the capturing unit which differ withregard to their respective field of view and in that the field of viewof the second capturing unit is adjustable due to the data captured bythe sub-units of the capturing unit being separately analysable and/ordue to the sub-units of the capturing unit being separatelycontrollable.
 22. The spectacle device according to claim 16,characterized in that the second capturing unit comprises at least onetwo-field lens and/or at least one progressive multi-focal lens and/orat least one prism and/or at least one free-form lens, in particular aconical mirror.
 23. The spectacle device according to claim 16,characterized in that the second capturing unit comprises a detectorwith a pixel array and the adjusting of the field of view is effected byselection of the pixels the data of which are captured.
 24. Thespectacle device according to claim 16, characterized in that the atleast one captured parameter concerns an orientation and/or a positionand/or an eyelid closure and/or a pupil diameter and/or limbuscharacteristic and/or a sclera characteristic and/or an irischaracteristic and/or a characteristic of a blood vessel and/or a corneacharacteristic of the at least one eye.
 25. The spectacle deviceaccording to claim 16, characterized in that the second capturing unitis integrally connected to the frame and/or structurally integrated inthe frame.
 26. The spectacle device according to claim 16, characterizedin that the frame comprises at least a first and a second frame element,wherein the second capturing unit is attached to the second frameelement, and wherein the second frame element is pivotably hinged to thefirst frame element, and wherein the first frame element is formed inparticular as an arm.
 27. A method for capturing at least one parameterof at least one eye of a test person by means of a spectacle device, themethod comprising the steps: optically capturing the at least oneparameter of the at least one eye by means of at least one firstcapturing unit; capturing an optical capturing range of a secondcapturing unit by means of the second capturing unit, wherein thisoptical capturing range corresponds at least partly to an opticalcapturing range of the at least one eye; outputting data concerning afield of view of the second capturing unit by the second capturing unit,wherein the field of view is correlated with the optical capturing rangeof the second capturing unit for a specific orientation of the spectacledevice in space, characterized by the following step: adjusting thefield of view of the second capturing unit by means of an adjustmentmeans of the spectacle device.
 28. The method according to claim 27,characterized in that the field of view is automatically adjusted independency on the at least one captured parameter of the at least oneeye.
 29. The method according to claim 27, characterized in that thefield of view is automatically adjusted in dependency on data concerningthe kind of an object captured by the second capturing unit and/or acharacteristic of the object and/or a distance of the object from thesecond capturing unit and/or an orientation of the object relative tothe second capturing unit.
 30. The method according to claim 27,characterized in that the field of view is adjusted in such a way thatby the set of the adjustable field of views a resulting field of view iscovered that essentially corresponds to the physiological field of viewof a human being.